One-dimensional and two-dimensional 1H- and 13C-nuclear magnetic resonance (NMR) analysis of vitamin E raw materials...

Two-dimensional spectral analysis (COSY, HETCOR) was utilized to make the complete 13C- and 1H-NMR assignments for alpha-, beta-, gamma-, and delta-tocopherol as well as for the acetate and succinate esters of alpha-tocopherol. 13C-NMR was found to be especially useful in distinguishing between the various tocopherols and distinguishing between the d-isomer and the d,l-racemic mixture. HETCOR spectra were also found to be useful for the qualitative identification of mixtures of the tocopherols and sesame oil. Using a procedure designed to minimize errors arising from spin relaxation and nuclear Overhauser effects, 13C-NMR peak integrals were used to quantitate alpha-tocopherol and delta-tocopherol in the presence of sesame oil using benzoic acid as the standard for calibration of the quantitation. The NMR results were compared to a capillary column gas chromatographic analysis of the individual alpha-tocopherol and delta-tocopherol reference materials.